Our long term goal in studies of the acetylcholine receptor is an understanding of the detailed molecular mechanism responsble for its control of ion permeabilities in excitable membranes. These studies require that the purified receptor protein be obtained in a state as close to the native functional state as possible. Since we have become convinced that chemical modifications of the receptor protein have been occurring during the initial electric tissue homogenization as well as during purification, the investigation of the conditions required for the isolation of the receptor which retains native structure and function is essential. Specifically, the feasibility of protecting reactive sulfhydryl groups and the inclusion of certain phospholipids in orde to stabilize the receptor will be studied. Kinetics of calcium-binding to the acetylcholine receptor will be studied using a stopped-flow spectrometry and agonist and antagonist mediated release and/or uptake of calcium from the receptor will be investigated. The specific covalent labelling of the receptor with fluorescent probes which respond to the addition of an agonist will be explored. If such labelling of the receptor is achieved, fast kinetics of acetlcholine binding will be studied by stopped-flow fluorometry.